Electrical resistance.



Patented Nov. 12, l90l.

J. F. BACHMANN &. A. VOGT.

ELECTRICAL RESISTANCE.

(Applicntion filed Nov. 22, 1898.)

(No Model.)

UNITE STATES PATENT OFFICE.

JOSEF FRANZ BACHMANN AND ADOLF YOGT, OF VIENNA, AUSTRIA- HUNGARY,ASSIGNORS TO THE ELECTRIC RESISTANCE AND HEATING CO. LTD. OF LONDON,ENGLAND.

ELECTRICAL RESISTANCE.

SPECIFICATION forming part of letters Patent No. 686,245, dated November12, 1901.

Application filed November 22, 1898. Serial No. 897,192. (No model.)

To all whom it may concern:

Be it known that we, J OSEE FRANZ BACH- MANN and ADOLF Voer, subjects ofthe Emperor of Austria-Hungary,residing at Vienna, in the Province ofLower Austria, in the Empire of Austria-Hungary, have invented certainnew and useful Improvements in Electrical Resistances; and we do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same, reference being had to theaccompanying drawings,and to letters of reference marked thereon, whichform a part of this specification.

This invention relates to electrical resistances made of anartificial-stone compound, such as is described in our application ofOctober 8, 1897, No. 654,560, which consists of a mixture of aconductor, such as carbon or metal, and a non-conductor, such as kaolinor oxids, such mixture being formed into a paste with water or otherliquid, and after molding or running the mixture into molds and dryingthe same heating the body to a' high temperature while it is eitherembedded n carbon powder or is surrounded by reduc- 1ng-gases.

The present invention relates to the manufacture of resistances oftubular or cylindrical form of such artificial-stone compound, wherebythe contact-surfaces between the said tubular resistances and thecircuit-clos ing devices thereof, while being of a 'very compact formare rendered comparatively extensive, and thus any such inaccuracy offit between parts'of such surfaces that are liable to occur withresistance-bodies of this nature is compensated for. A still greateraccuracy and compactness of contact is insured in some of theconstructions of such tubular resistances by making the contactsurfacesboth of the resistance-body and the circuit-closing device withscrew-threads, so

that the position of the contact-closing device relatively to theresistance-body is determined by screwing the one part upon the otherpart in one direction or the other, while such screwing action alsoinsures a more ac-' curate fit and also affords a considerably-increasedextent of the contact-surfaces.

On the accompanying drawings are shown, by way of example, variousconstructions of tubular resistance-bodies according to our invention.

Figure 1 shows averti'cal section, and Fig. 2 a sectional plan, of atubular resistancebody a, made of the before-mentioned artificial-stonecompound, to the upper and lower ends of which are connected ring-shapedcontact-clamps b, to which the wire-leads of an electric circuit areattached, so that the current has to pass from the one contact 1)through the resistance a to the other contact I). It will be seen thatby means of its tubularform this resistance-body is made to afford acomparatively large amount of contactsurface for the contact-clamps b ina very compact'form; also, that the degree of resistance, offered to thecurrent can be readily adjusted to any required amount by shifting theone or other contact-clamp nearer to or farther from the other one. Theresistancebody may be held in any suitable insulated manner, such as bythe insulated clampingbracket a: shown.

The tubular resistance-body a may either be smooth externally andinternally, as shown at Figs. 1 and 2, or it may be provided eitherinternally, as at the cross-section, Fig. 3, or externally, as at Fig.4, with ribs or other projections for facilitating the cooling of theresistance by radiation. The external projections would of course onlybe made on the parts of the resistance body between the points where thecontact-clamps b are at tached. I

Fig. 5 shows a vertical section of a tubular resistance-body having ascrew-thread formed on'its outer surface, and the ringshapedcontact-clamps b are in like manner formed with an internalscrew-thread, so that 1 they can readily be screwed toward or away fromeach other for adjusting the resistance offered to the current. Thescrewthreads on the resistance-body and contacts might be made right andleft handed, so that by turning the former instead of the contact-clampsthe latter would be screwed nearer together or farther apart.

Fig. 6 shows a vertical section of a tubular resistance a formed with aninternal screwthread, into which screws a threaded 'piston b ofconducting material, which constitutes the one contact of the circuit,the piston I) being fixed on a screw-spindle d, screwing through aconducting-disk d, to which the lead of the circuit is attached. Thethread of the spindle at being made of the same pitch as that of thepiston b it will be seen that the contact-plate d this may be loose fromthe resistance a and arranged to act as a screw-nut-that is to say, whenit is desired to shift the piston b the nut d is first screwed downwardon spindle d and after then turning this so as to shift the piston thenut d is screwed up against a so as, by tending to draw (1 downward, tocause the thread of b to be pressed tightly against the thread of a, andthus insure reliable contact.

Fig. 7 shows an elevation, and Fig. 8 a crosssection, of an arrangementin which there are two tubular resistances a a connected together,having the one double contact-clamp b attached'to the lower end, whilethe other contact b is formed so as to be shiftedup or down upon theresistance-body .by means of the screw-spindle d, which screws through athreaded hole in the middle part of the contact b.

Instead of making the resistance-bodies a as cylindrical tubes they mayof course also be made of a square or polygonal cross-section, as atFig. 9, or they may be of a trough or H shaped section, as at Figs. 10and 11, the contacts being of course made of a corresponding shape tofit the resistance-body. The two resistances may be connected togethereither in parallel or in series in the circuit.

For resistances of large dimensions, such as those required for theatersand the like, the resistance-body may be formed as a cylindor ofcomparatively large diameter relatively to its length, as shown in thevertical section'at Fig. 12, where thecylindrical resistance a has afixed contact b at its upper end, while the second contact is inthe formof a piston b, fitting the interior of a accurately and adjusted inposition by means of the rod 01, to which the. second lead of thecircuit is attached. For facilitating the cooling' of the resistance athis may either be formed with external ribs or projections, as shown atthe cross-section, .Fig. 13, or it may have passages formedlongitudinally through it, as shown in the cross-section at Fig. 14. Inthis case air or suitable cooling liquid under more or less pressure canbe made to flow through the said passages for effectually cooling theresistance, such liquid being conveyed to the said passages by conduit-sconnected to the ends of the resistance in any suitable known manner.For the same purpose the cylindrical resistance at Fig. 12 may beprovided with an external jacket through which cooling air or liquid ismade to flow. The piston-contact b may also be made with holes throughit for the passage of cooling-air. Such cooling devices are ofconsiderable importance for large resistances, such as are requisite intheaters and the like, in which a considerable amount of heat isdeveloped, as by the above cooling means the danger of fire iseffectually avoided.

In all the above constructions those parts of the resistance-bodies thatdo not serve as contacts or the channels formed therein can be coatedwith a suitable glaze.

Having thus described the nature of this invention-and the best means weknow of carrying the same into practical effect, we claim 1. Anelectrical resistance,comprisinga hollow, open-ended resistance-body, acircuit ter minal contact at one end of the body and an annular orpiston-like terminal contact shiftable Within said body, for the purposeset forth.

2. An'electrical resistance,co1nprlsing a hol= low'open-endedresistance-body, means for cooling said body, a circuit terminal contactat one end of the body and an annular or piston-like terminal contactshiftable within the body, for the purpose set forth.

3. An electrical resistance,comprisinga hollow resistance-body providedwith a screwvthread extending lengthwise thereof, a circuit terminalcontact at one end of said body and a second circuit terminal contactfitting said screw-thread, for the purpose set forth.

4. An electrical resistance,comprisinga hollow openended resistance-bodyprovided with a screw-thread extending lengthwise thereof, a circuitterminal contact at one end of said body and a second circuit terminalcontact fitting said screw-th read, for the purpose set forth.

5. An electrical resistance comprising a tubularinternally-screw-threaded resistancebody, a circuit terminal contact atone end of said body and a second circuit terminal contact fitting theinternal screw-thread of said body, for the purpose set forth.

6. An electrical resistance,comprisinga hollow open-endedresistance-body of an artificial-stone compound, composed of a mixtureof conductive and non-conductive substances,

and provided with a screw-thread extending at one' end of said body anda second circuit terminal contact fitting said thread, for thepurposeset forth.

7. An electrical resistance, comprisinga tubular resistance-body of anartificial-stone I compound, composed of conductive and nonconductivesubstances and having a screwthread extending lengthwise thereof, andheat-radiating ribs, a circuit terminal contact at one end of said bodyand a second circuit terminal contact fitting said screw-thread, for thepurpose set forth. I

In testimony that we claim the foregoing as our invention we have signedour names in 15 presence of two subscribing witnesses.

JOSEF FRANZ? BACHMANN. ADOLF VOGT.

Witnesses:

ALVESTO S. HOGUE, AUGUST FUGGER.

